Description

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Advanced · 13 min

Generators

Produce values lazily with yield and consume them as needed.

Yield one value at a time

A generator pauses at yield and resumes on the next request. It avoids building the whole result list first.

def countdown(start):
    while start > 0:
        yield start
        start -= 1

print(list(countdown(3)))

Output

[3, 2, 1]

Build a pipeline

Generator expressions are lazy. Functions such as sum() can consume their values directly.

numbers = [2, 3, 4]
squares = (number ** 2 for number in numbers)
print(sum(squares))

Output

29

Generators

  1. Read both generators examples before answering.
  2. Run the task, compare its exact output, and revise the code if needed.

Try it yourself

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Generate even numbers

Complete evens(limit) so it yields the even numbers from 0 through limit. Display the supplied list.

Practice